A reflector plate is used in various situations in order to use light efficiently. In recent years, the switchover of a light source to a semiconductor-based one, that is, to a semiconductor laser or a light emitting diode (hereinafter referred to as LED) for the reduction in the size of an apparatus and a light source has been advancing. Therefore, the reflector plate is required to have not only mechanical strength, but also good heat resistance and precision moldability because it is, for example, surface-mounted on a printed-circuit board or the like. The reflector plate is also required to have stable high reflectance because of its function to reflect light, and in particular, it is necessary to suppress the reduction in reflectance due to heating in the steps of assembling LED and reflow soldering.
Further, cost reduction requirements for products have been increasing in recent years. The number of LED packages to be mounted on a finished product such as TV and a monitor is reduced, and the luminance is increased accompanying it. In addition, the reduction in the size of a product is also required. Therefore, cost reduction is achieved by increasing the number of obtainable parts in the production of LED packages by injection molding. In addition, there is required a molding material which not only offers improvement in reflectance but has high melt-flowability.
Glass fibers are generally used in wide applications as a reinforcing material (inorganic filler). However, for example, in the case of molding in which a large number of small molded articles are molded by one shot of injection molding from a molding material containing glass fibers, melt-flowability may tend to be insufficient. Further, a molded article of a molding material containing glass fibers may have a coarse gate cut surface, and since the area ratio which a gate cut surface occupies is relatively large particularly in a small-sized product, the coarse gate cut surface may significantly reduce product appearance. Therefore, an improvement in the melt-flowability of a molding material containing an inorganic filler is required.
Various improvements have been attempted in order to solve this problem. Examples of inorganic fillers particularly shown include Wollastonite (PTL 1), a potassium titanate-containing compound (PTL 2), and a combined use system of potassium titanate and titanium oxide (PTL 3).
However, there is concern that these techniques cause a reduction in reflectance and a reduction in mechanical strength due to the poor dispersion of an inorganic filler in a base polymer by using a plurality of inorganic fillers. Further, in order to disperse an inorganic filler in a base polymer, special screw configuration and temperature setting are used in melt mixing, which increases a load to the base polymer. This may pose the problem of causing a reduction in function due to the decomposition of the base polymer or easily leading to a cost increase.
On the other hand, a technique of suppressing a reduction in reflectance by the improvement of a base polymer is also shown (PTL 4). In many examples, a polyamide material is used for a reflector plate, but discoloration derived from a terminal amino group or an amide bond may occur, resulting in causing a reduction in reflectance. On the other hand, a heat-resistant polyester is attempted to be used instead of a polyamide resin. However, there is no disclosure with respect to the flowability of a resin composition containing a heat-resistant polyester as a base polymer and the mechanical strength of the molded article, and the performance balance as a reflection material is unknown.